Intermediate Soil Research Articles

Examining intermediate soil properties variability through spatial interpolation methods in GIS

This study compares Kriging and Inverse Distance Weighting (IDW) spatial interpolation methods for estimating intermediate soil properties at a construction site in Astana, Kazakhstan. Using data from eight boreholes, seven engineering geological elements (EGE) were identified and analyzed at 6.5 m and 11.5 m depths. Kriging produced deformation modulus values ranging from -0.29 to 18.99 MPa at 6.5 m and -0.51 to 23.94 MPa at 11.5 m, capturing more spatial variability compared to IDW, which provided ranges of 3.3 to 18.99 MPa and 2.6 to 23.99 MPa, respectively. Kriging’s ability to account for spatial correlations resulted in more accurate predictions, particularly in areas with complex subsurface variability. Meanwhile, IDW offered reliable localized results, effective in more uniform geological conditions. The findings demonstrate that both methods are valuable for geotechnical applications, with the choice depending on data density and site variability.

Plant growth and physiological responses of the invasive plant Acmella radicans to contrasting light and soil water conditions

Acmella radicans (Jacquin) R.K. Jansen is a new invasive species record for Yunnan Province, China, as of 2017 and little is known about its invasion mechanisms. To better understand its invasive strategies, we investigated the growth, physiological and soil nutrient use parameters of the invader under combined conditions of light (25%, 50%, 75%, and 100% of light availability) and soil water content (full, high, medium, and low soil water content) in the glasshouse. The results showed that light level, soil water content and their interaction had a significant effect on all plant morphological, physiological and soil nutrient parameters for A. radicans (P < 0.05). For the most part, plant height, total branch length, leafstalk length, leaf area, inflorescence number, seed number, leaf biomass, stem biomass, aboveground biomass, and total biomass of A. radicans were significantly increased with increased shading rate and soil water content and were generally greater at intermediate light levels and intermediate to high soil water levels. Under high-irradiance conditions, the chlorophyll content was greatly reduced compared to other treatments. We also observed that leafstalk length, leaf area, Pn, chlorophyll a, and chlorophyll b of A. radicans were markedly increased with increased shading rate and soil water content, and were generally highest under intermediate irradiance and soil water conditions, but many plant physiological parameters also exhibited relatively high values under waterlogging conditions. The concentrations of organic matter, available N and available K of A. radicans soils at high-irradiance and full-high soil water content treatments and medium-irradiance and high-medium soil water content treatments were often less than those of other treatments indicated that hypothetically soil absorption was increased by moderate shading and high soil water. This was the first study demonstrating that A. radicans thrives best under moderate light conditions in combination with high soil water. Furthermore, we surmised that its higher phenotypic and physiological plasticity contributes to its invasion success.

Temporal variations in burn severity among various vegetation layers in subtropical Pinus Roxburghii (Chir Pine) forest of Hindu Kush mountain range

The Sub-tropical forests of Pinus roxburghii (chir pine) provide various ecosystem services and act as watershed for low lying regions. However, this species is prone to human induced fire primarily due to local communities' dependence for various resources exacerbated by the current dry conditions. The impact of fire across various vegetation layers and developmental stages has not been thoroughly studied. Bearing to this, the present study was conducted using composite burn index to assess the severity on various layers of vegetation and their long-term impact through a chronological approach. The impact of fire on 40 representative circular plots with a radius of 30 m, categorized into five forest strata: large and intermediate trees, seedlings/saplings, pole stage, shrubs, and soil were investigated and compared across four different time interval: unburnt (B0), burnt two years ago (B2), burnt five years ago (B5), and burnt 15 years ago (B15). The results were statistically proved using Kruskal–Wallis followed by Dunn's Post Hoc and Friedman test with the Holm correction in R Language. The study revealed significant variations in the average burn severity for each treatment, with shrubs having the highest average score of burn severity (average = 1.4) and soil showing the lowest (average = 0.408). The results of the Friedman test indicated non-uniform distribution of burn severity across different ecological treatments. This study is contributing significant insights into the effects of forest fires and their severity on different vegetation layers, which can be instrumental in devising and executing successful restoration strategies.

New Design Criteria for Long, Large-Diameter Bored Piles in Near-Shore Interbedded Geomaterials: Insights from Static and Dynamic Test Analysis

This paper presents an analysis of long, large-diameter bored piles’ behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors φqp, φqs, and φload were proposed to be 0.65, 0.70, and 0.80, respectively.

Multi-scale assessment of a cosmic-ray neutron probe observation of soil moisture for surface layer applications in a mountainous forest environment

Soil moisture is critical to the Earth's water cycle as it influences water exchange between the land, atmosphere, and oceans. This study assessed the potential of a cosmic-ray neutron probe (CRNP) to monitor soil moisture dynamics in a forested mountain region, which is critical for water resource management and ecosystem health. Accurate soil moisture monitoring is essential for effectively managing forested mountainous areas, but various limitations exist in such environments. To overcome the complexities of soil moisture monitoring, an observatory consisting of a CRNP, automatic weather sensors, and dataloggers was established. Fifteen capacitance sensor (CS) stations were placed strategically within the CRNP's footprint to ensure strict evaluation. Although each CS measurement revealed the heterogeneity of the experimental site, temporal stability analysis determined the representative soil moisture. The validation of the CRNP and the average results of the 15 surface CS sensors revealed that they were strongly correlated (R = 0.94). It means that the CRNP can describe the dynamics of soil moisture that fluctuate according to physical properties, underscoring its reliability in estimating intermediate scale soil moisture. This correlation remained robust despite differences in rainfall patterns over three years. These findings indicate that the CRNP may be a valuable tool for monitoring soil moisture in a challenging environment. Additionally, the evaluation of the Advanced Microwave Scanning Radiometer-2 (AMSR2), Advanced Scatterometer (ASCAT), and Global Land Data Assimilation System (GLDAS) demonstrated the usefulness of CRNP in supplying reference data. The AMSR2 showed an inadequate temporal pattern (R = 0.35), and the ASCAT achieved the highest correlation agreement (R = 0.67) with the CRNP. The GLDAS also showed close agreement, although with some discrepancies (R = 0.52). The results of this study support the utilization of CRNP and provide insight into establishing and expanding a soil moisture network.

Increases and decreases in soil moisture in water‐limited plant communities cause asymmetrical responses in biomass but not in diversity

AbstractAimsChanges in precipitation patterns, such as the predicted increases in the frequency of climatic extremes, are likely to alter plant communities, but whether responses to drought or to wetter conditions respectively cause consistent, opposite responses is debated. Here, we assessed the response in biomass production and species diversity of water‐limited plant communities to the direction (increase or decrease) and magnitude (micro‐ and macro‐climatic effects) of changes in soil moisture.LocationWe reciprocally translocated soils containing seed banks from two climates (semi‐arid and mediterranean) at a micro‐climatic (opposite slopes) and a macro‐climatic scale (between climates) in Chile.ResultsBiomass production for the soils that were translocated from wetter to drier climates was unrelated to the available soil moisture. The lowest biomass was produced in the wettest climate on the wet slope. Biomass production increased after a translocation to the drier climate (representing the largest change in climate). Nonetheless, the highest overall biomass for the wet to dry translocation was produced on the mediterranean dry slope with intermediate soil moisture. However, on the same mediterranean dry slope, biomass was almost zero for soil translocated the other way round (from drier to wetter). Diversity after 24 months was unaffected by micro‐climatic change, but soils transplanted toward the drier climate yielded a plant community with increased diversity.ConclusionOur results showed direction and magnitude of climate change but also the response factor that is studied matters to detect direction‐dependent responses; i.e., species richness had a linear and reversible response. However, the response of biomass depended on the origin of the transplanted material (soil and plant community), indicating history dependence (hysteresis). This emphasizes that responses to unidirectional climate manipulation experiments may not be able to capture the entire nature of the response of plant communities to climate change.

Highly alkaline electrokinetic extraction: Characteristics of chromium mobilization, conversion and transport in high alkalinity soil

In site chromium (Cr) contaminated soil characterized by high alkalinity and carbonate content, protons are not effectively targeted for Cr(III) mobilization but rather accelerate the reduction of easily transportable Cr(VI) within the acidification electrokinetic (EK) system. As an alternative, the highly alkaline extraction conditions (HAECs) maintained by anolyte regulation are explored owing to the ability to desorb strong binding Cr(VI) and form anionic Cr(III)-hydroxides (Cr(OH)4−, Cr(OH)52−). The results demonstrate that HAECs were more efficient in mobilizing ions in severe alkalinity and electrical conductivity soil compared to organic acid acidifying extraction conditions (OAECs). Simultaneously, a limited amount of soluble Cr(III) was produced; however, its transportation was hindered and more noticeable in the case of Cr(VI), displaying a distinct retention phase within the intermediate soil chamber. The antagonistic interplay between electromigration and electroosmotic flow was considered the main responsible factor. The conversion intensity of Cr(VI) to Cr(III) was inhibited at HAECs. The promising mobilization and low conversion intensity contributed to total Cr removal. At HAECs, enhanced electromigration and electroosmotic flow combined with a favorable oxidation environment may facilitate in situ delivery of oxidants, offering practical implications for the EK detoxification of high alkalinity site soil contaminated with Cr. The practicability of HAECs is likely to be enhanced when the cost-benefit balance of providing a simultaneous energy supply during site treatment is resolved.

Tree growth potential and its relationship with soil moisture conditions across a heterogeneous boreal forest landscape

Forest growth varies across landscapes due to the intricate relationships between various environmental drivers and forest management. In this study, we analysed the variation of tree growth potential across a landscape scale and its relation to soil moisture. We hypothesised that soil moisture conditions drive landscape-level variation in site quality and that intermediate soil moisture conditions demonstrate the highest potential forest production. We used an age-independent difference model to estimate site quality in terms of maximum achievable tree height by measuring the relative change in Lorey’s mean height for a five year period across 337 plots within a 68 km2 boreal landscape. We achieved wall-to-wall estimates of site quality by extrapolating the modelled relationship using repeated airborne laser scanning data collected in connection to the field surveys. We found a clear decrease in site quality under the highest soil moisture conditions. However, intermediate soil moisture conditions did not demonstrate clear site quality differences; this is most likely a result of the nature of the modelled soil moisture conditions and limitations connected to the site quality estimation. There was considerable unexplained variation in the modelled site quality both on the plot and landscape levels. We successfully demonstrated that there is a significant relationship between soil moisture conditions and site quality despite limitations associated with a short study period in a low productive region and the precision of airborne laser scanning measurements of mean height.

CPT calibration chamber testing on tailings

The cone penetration test (CPT) is a widely used technique for on-site investigations. In the field, interpretation correlations of CPT can be established using laboratory calibration chamber tests. Empirical and theoretical correlations were developed for clay and sand under undrained and drained conditions, respectively. However, interpreting these results can be more challenging for intermediate soils that exhibit partial drainage during penetration and lie between fully undrained and drained conditions. Tailings, which are the by-products of mining and are often rich in fine particles, are a typical example of such intermediate soils. To gain a deeper understanding of the behavior of the tailings during CPT, a calibration chamber test was performed at a standard rate of 2 cm/s and subsequently at a slow rate of 0.02 cm/s, and the obtained results were analyzed.

Intermediate soil acidification induces highest nitrous oxide emissions

Global potent greenhouse gas nitrous oxide (N2O) emissions from soil are accelerating, with increases in the proportion of reactive nitrogen emitted as N2O, i.e., N2O emission factor (EF). Yet, the primary controls and underlying mechanisms of EFs remain unresolved. Based on two independent but complementary global syntheses, and three field studies determining effects of acidity on N2O EFs and soil denitrifying microorganisms, we show that soil pH predominantly controls N2O EFs and emissions by affecting the denitrifier community composition. Analysis of 5438 paired data points of N2O emission fluxes revealed a hump-shaped relationship between soil pH and EFs, with the highest EFs occurring in moderately acidic soils that favored N2O-producing over N2O-consuming microorganisms, and induced high N2O emissions. Our results illustrate that soil pH has a unimodal relationship with soil denitrifiers and EFs, and the net N2O emission depends on both the N2O/(N2O + N2) ratio and overall denitrification rate. These findings can inform strategies to predict and mitigate soil N2O emissions under future nitrogen input scenarios.

Geotechnical interpolation methodology for determining intermediate values of soil properties

The article considers the application of geotechnical interpolation using ArcGIS software to determine the intermediate geotechnical properties of soils at a construction site in a residential complex in Astana, Esil district. The study is based on data from 8 boreholes drilled to a depth of 26 meters, and the purpose of the work is to use the kriging interpolation method to determine intermediate soil properties. The raw data include the results of analyzing the physical and mechanical properties of the soils from the boreholes, which served as a basis for interpolation and mapping. The results of the study are presented in the form of maps showing the intermediate mechanical properties of the soil at depths of 5, 10 and 15 m. The maps allow obtaining more accurate intermediate values. The proposed methodology not only facilitates the work of designers, but also provides data for realistic scenarios of soil strength and deformation characteristics, which significantly influences the selection of optimal types and sizes of foundations.

Landfill intermediate cover soil microbiomes and their potential for mitigating greenhouse gas emissions revealed through metagenomics

Landfills are a major source of anthropogenic methane emissions and have been found to produce nitrous oxide, an even more potent greenhouse gas than methane. Intermediate cover soil (ICS) plays a key role in reducing methane emissions but may also result in nitrous oxide production. To assess the potential for microbial methane oxidation and nitrous oxide production, long sequencing reads were generated from ICS microbiome DNA and reads were functionally annotated for 24 samples across ICS at a large landfill in New York. Further, incubation experiments were performed to assess methane consumption and nitrous oxide production with varying amounts of ammonia supplemented. Methane was readily consumed by microbes in the composite ICS and all incubations with methane produced small amounts of nitrous oxide even when ammonia was not supplemented. Incubations without methane produced significantly less nitrous oxide than those incubated with methane. In incubations with methane added, the observed specific rate of methane consumption was 0.776 +/− 0.055 μg CH4 g dry weight (DW) soil−1 h−1 and the specific rate of nitrous oxide production was 3.64 × 10−5 +/− 1.30 × 10−5 μg N2O g DW soil−1 h−1. The methanotrophs Methylobacter and an unclassified genus within the family Methlyococcaceae were present in the original ICS samples and the incubation samples, and their abundance increased during incubations with methane. Genes encoding particulate methane monooxygenase/ ammonia monooxygenase (pMMO) were much more abundant than genes encoding soluble methane monooxygenase (sMMO) across the landfill ICS. Genes encoding proteins that convert hydroxylamine to nitrous oxide were not highly abundant in the ICS or incubation metagenomes. In total, these results suggest that although ammonia oxidation via methanotrophs may result in low levels of nitrous oxide production, ICS microbial communities have the potential to greatly reduce the overall global warming potential of landfill emissions.

Vegetation restoration strategies based on plant water use patterns

The study on the water source of plants in alpine mountainous is of great significance to optimize the allocation and management of water resources, and can also provide important reference for ecological restoration and protection. However, the controls of water sources for different plants in alpine mountainous region remain poorly understood. Based on the advantages of stable isotope tracer and Bayesian (MixSIAR) model, the water source of plants in Qilian Mountains was quantitatively analyzed. The results showed that the water sources of plants in Qilian Mountain mainly included two parts: direct source and indirect source. The direct source is soil water, which provides most of the water that plants need. The highest contribution of soil water to shrubs was 80 %, followed by trees (73 %) and herbs (72 %). It is worth mentioning that trees mainly use deeper soil water (below 60 cm), shrubs mainly use surface and intermediate soil water (0-60 cm), and herbs mainly use surface soil water (0-40 cm). What is more noteworthy is that indirect sources, such as precipitation, glacier and snow meltwater, and groundwater, are also water sources that cannot be ignored for plant growth in study area. Shrubs and Herbs use more soil water in the range of 40-60 cm, which leads to the possibility of water competition between these two planting types. Therefore, attention should be paid to this phenomenon in the process of vegetation restoration and water resources management. Especially when planting or restoring artificial plants, it is necessary to consider the water use strategy of the two plants to avoid unnecessary water competition and water waste. This is of great significance for ecological stability and sustainable utilization of water resources in the study region.

Bearing Capacity of a Shallow Foundation above the Soil with a Cavity Based on Rigid Plastic Finite Element Method

Based on the Rigid Plastic Finite Element Method (RPFEM), this study investigates the performance of the footing on the soil with a cavity. The RPFEM is used in plane strain conditions and necessitates only a few materials to predict the bearing capacity: the unit weight of the soil, the cohesion, the shear resistance angle, and the dilation angle. Considering diverse soil types, including cohesive and intermediate soils, the findings are presented through dimensionless 2D charts in which the horizontal axis X and vertical axis Y are normalized to parameters R and H, representing the horizontal and vertical dimensions of the plastic mechanism beneath the footing in the absence of the soil cavity. Analyzing geometric factors such as footing width B and cavity characteristics (shape, size, and location), the study reveals that the farther the cavity, the less it impacts the footing performance. The distribution of the normalized bearing capacity across the (X, Y) space elucidates the expansion and variation of the influence zone. Equations incorporating the mentioned geometric parameters and soil shear strengths are proposed and verified with data in the literature. In cohesive soils, the influence zone predominantly extends vertically, following the expansion of the slip surface in no void condition. Conversely, for intermediate soils, the zone of influence exhibits a dependency on the shear resistance angle, resulting in an extension in one direction more than the other. Illustrating typical failure mechanisms, the study delves into detailed discussions to enhance comprehension of how the cavities affect the bearing capacity of the footing.

Dynamic hydrological niche segregation: How plants compete for water in a semi-arid ecosystem

Hydrological niche segregation (HNS), specifically the variation in root water uptake depth among coexisting species, is an understudied area of research. This is especially the case in semi-arid ecosystems, such as China’s Loess Plateau (CLP), where seasonal aridity necessitates adaptive water use strategies among plant species. In this study, we conducted a two-year investigation to understand the water sources and intrinsic water use efficiency (WUEi) of four coexisting plant species: Populus simonii (tree), Caragana korshinskii and Salix psammophila (shrubs), and Artemisia ordosica (semi-shrub). We analyzed the isotopic compositions of xylem and soil water (δ2H and δ18O) and leaf δ13C to identify the water sources and WUEi, respectively, of each species. We then used the nicheROVER model to quantify HNS based on the variations in xylem water δ2H and δ18O. Our results show that the four co-existing species occupied distinct positions on a hydrological niche axis, delineated by their respective water sources and disparate WUEi. The tree P. simonii exhibited a preference for deep soil water and demonstrated a high WUEi. Both shrubs, S. psammophila and C. korshinskii, utilized intermediate and deep soil water, respectively, and with comparable WUEi. Conversely, the semi-shrub A. ordosica relied on shallow soil water and displayed a low WUEi. These differences in water sources and WUEi led to HNS between A. ordosica and the other three species in a relatively wet year. However, in a relatively dry year, HNS between A. ordosica and the other three species contracted and WUEi increased as species increased the use of deep soil water. Overall, these results demonstrate that HNS is a dynamic phenomenon that varies on at least an annual basis. It expands and contracts as plants regulate their water uptake and loss in response to changing soil moisture conditions.

Comparison between methods for determining the effective vertical yield stress of intermediate fine-grained soils.

Effective vertical yield stress (σ'xy) is essential in accurately describing fine-grained soils' mechanical properties and their behaviour under load over time. It helps assess settlements and stress history. In most constitutive models, this parameter indicates changes in the soil behaviour due to the development of recoverable and irrecoverable strains resulting from loading. The results of oedometric compression tests for 25 soil samples with a wide range of plasticity parameters were used for the investigation. The intermediate fine-grained soils comprised different proportions of clayey, silty and sandy fractions. An in-depth, two-staged statistical analysis was carried out to compare twelve methods of determining effective vertical yield stress, namely: Casagrande (CM), Pacheco Silva (PSM), Butterfield (BTM), Oikawa (OIM), Onitsuka (ONM), Boone (BM), Becker (WM), Morin (WPUVSM) Wang & Frost (DSEM), Tavenas (SEM), Senol (SLSEM), and Janbu (JM). It aimed to check the association of these methods and the consistency of the obtained results. Based on the difference analysis, the methods originated in the work approach (i.e. WM, WPUVSM, DSEM) and CM gave comparable σ'xy values. The methods utilised bi-logarithmic plots (i.e. BTM, OIM, ONM) received slightly greater or lesser σ'xy values than BM and JM. The remaining methods were characterised by medium to the high variability and were sensitive to even the slightest disturbances resulting from the procedure of determining σ'xy.

The sinkholes and their appearance in the karstic zones

The objective of this work was to study the sudden appearance of a sinkhole in the town of Los Angeles, belonging to the municipality of Rioverde S. L. P., to avoid damage to the patrimony of the families and infrastructure of the city. The research work consisted of 6 stages: Stage 1, a site visit to gather information about the place and obtain the impressions of the neighbors of the area of analysis (street crossing); Stage 2, sought to verify the topography of the site and locate the sources of humidification or bodies of water; Stage 3, consisted of the exploration using the manual dynamic penetrometer (MDP) and the recovery of the integral and unaltered sampling of the site; Stage 4, included the development of conventional geotechnical tests for the characterization of the soils present, determine their moisture profile, as well as determine the possibility of dispersion, piping, and collapse. In Stage 5, the stress distribution in the subsoil was modeled and in Stage 6, the conclusions are presented. Through the MDP, an infiltration point was identified at the intersection of the streets of the study site, a frustoconical hollow with a depth of 2.80 m, with an upper diameter of 0.80 m and a lower diameter of approximately 2.00 m, was located. The depth of the GWL in the water extraction wells in the area is 12 m, the soil of the place has low Penetration Resistance up to a depth of 4.80 m. Subterranean conduits were identified that branch off in different directions, predominantly in a northeasterly direction. The stratigraphic profile of the place corresponds to the following sequence of five strata found at a maximum explored depth of 6.00 m; the first layer is an inorganic clay of low plasticity (CL), and from the second to the fifth layer there are inorganic silts of low compressibility (ML). The second stratum is an intermediate grade dispersive soil, with appreciable strength and little deformation at its natural moisture content, however, when hydrated it experiences a slight propensity to collapse and is susceptible to erosion.

OPTIMIZATION OF NITROGEN FERTILIZATION FOR AGRICULTURAL CROPS UPON ADDITIONAL APPLICATION OF FRESH ORGANIC MATTER TO THE SOIL

Objective. Using biological testing, determine the environmental appropriate rates of mineralnitrogen, applied in the background of effect and aftereffect of straw and biomass of intermediatelupine green manure, in the fertilization system of potatoes and spring barley. Methods. Field experiment (growing crops in crop rotation in the conditions of a long-term (since 2009) stationaryexperiment on leached chornozem); gas chromatographic (to determine the potential nitrogenfixing (nitrogenase) and potential denitrifying activities in the rhizosphere soil of plants dependingon the fertilizer); statistical. Results. With the systematic application of fresh organic matter to thesoil in the form of 5.0 t/ha of straw and 5.3 t/ha of dry biomass of intermediate lupine green manure, the excess of nitrogen mineral compounds is metabolically bound (immobilized) by microorganisms, the process of nitrogen fixation is restored, the emission of N2O decreases, and the ratesof mineral fertilizers not exceeding N80P80K80 become environmentally appropriate when growingpotatoes. At the same time, the introduction of straw does not require additional provision of mineral nitrogen to optimize the C/N ratio. The highest rate of mineral fertilizers N120P120K120 in theexperiment, even when combined with organic matter for a long time is environmentally inappropriate — only at the end of the growing season, the studied indicators demonstrate its acceptability.When growing spring barley on leached chornozem, the optimization of the processes of biologicaltransformation of nitrogen compounds is achieved if mineral fertilizers are applied on the background of aftereffect of organic matter in a rate not exceeding N60P60K60. Systemic application ofN90P90K90 suppresses the activity of nitrogen fixation and ensures significant losses of nitrous oxide.This rate of fertilizers should be applied only on the condition that it is applied against the background of the aftereffect of straw and green manure mass, which contributes to the mitigation ofenvironmental consequences. Conclusion. The use of mineral fertilizers against the backgroundof systematic application of winter wheat straw and intermediate lupine green manure biomass tothe soil contributes to the optimization of the biological state of the leached chornozem. The improvement of environmental indicators contributes to the growth of the yield of agricultural crops.

Combined effects of soil 3D spatial heterogeneity and biotic spatial heterogeneity (plant clumping) on ecosystem processes in grasslands.

Soil heterogeneity has been shown to enhance plant diversity, but its effect on grassland productivity is less clear. Even less is known about the effect of plant clumping (intraspecific aggregation) and its potential interaction with soil heterogeneity. The combined effects of soil 3D spatial heterogeneity and species clumping were experimentally studied in grassland mesocosms consisting of four grassland species. These species were planted in three patterns (i.e. completely mixed, clumped by 9 or 36 individuals of the same species) on soils with heterogeneous cells of alternating nutrient-poor and rich soil differing in size from 0 (mixed soil) to 12, 24, and 48 cm (complete poor or rich mesocosm). Moderate soil cell sizes (12-24 cm) consistently increased whole-mesocosm aboveground productivity by more than 20%, which mainly originated from the increased growth of the plants growing on the poor soil cells. In contrast, total mesocosm productivity was not affected by species clumping although there were some species-specific effects, both of clumping and of the interaction of clumping with soil heterogeneity. Our results show that intermediate soil heterogeneity promotes productivity. Clumping can improve the growth of inferior species, thus promoting coexistence, without affecting overall productivity. We found no interaction effect of clumping and soil heterogeneity on productivity at the community level and some minor species-specific effects.

Determination of critical state line (CSL) for silty-sandy iron ore tailings subjected to low-high confining pressures

The disposal of filtered tailings in high dry stacks can induce particle breakage, changing the material's behaviour during the structure's lifetime. The grading changes influence material properties at the critical state, and this is not mature for intermediate artificial soils (tailings) in a broad range of confining pressures. In this paper, it aims to describe the behaviour of iron ore tailings in a spectrum of confining pressures broader than the reported in previous studies. A series of consolidated drained (CD) triaxial tests was carried out with confining pressures ranging from 0.075 MPa to 120 MPa. These results show that the amount of breakage plays an essential role in the response of iron ore tailings. The existence of curved critical state line (CSL) in both specific volume (ν)–logarithm of mean effective stress (p′) and deviatoric stress (q)–mean effective stress (p′) planes, and different responses in the deviatoric stress–axial strain–volumetric strain curves were verified. An inverse S-shaped equation was proposed to represent the silty-sandy tailings' behaviour up to high pressures on ν–lnp′ plane. The proposed equation provides a basis for enhancing constitutive models and considers the evolution of the grading up to severe loading conditions. The adjustment considered three regions with different responses associated with particle breakage at different pressure levels.